HomeSearch by dateVacation packagesHotelsFlight dealsCar rentalTravel tips & news

Cheap flights from Ontario to St. Louis (ONT - STL) from $73

This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 6/20. Fares are subject to change and may not be available on all flights or dates of travel. Click the price to replicate the search for this deal.
ONT — STL
Jun 14 — Jun 211
From?
To?
Fri 6/14
Fri 6/21
1 adult, Economy
We work with more than 300 partners to bring you better travel deals

The best prices from Ontario to Lambert-St Louis are usually found in October or November, booked 36 days in advance, depart on a Saturday or Wednesday and return on a Thursday

Cheap flight deals from Ontario to St. Louis

Discover tips and strategies to find the most affordable flight options for your journey from Ontario (ONT) to St. Louis (STL). Learn about various techniques such as flexible date searches, comparing prices across and setting up price alerts. Use these methods to find the cheapest flights available for your travel needs. Data last updated June 9, 2024.

Popular in

December

Cheapest in

October

Round-trip from

$318

One-way from

$197
High demand for flights, 39% potential price rise
Search Deals
Best time to find cheap flights, 29% potential price drop
Search Deals
From Ontario to Lambert-St Louis
Search Deals
One-way flight from Ontario to Lambert-St Louis
Search Deals

What is the cheapest day to fly round-trip from Ontario to St. Louis?

Leaving on a Friday is a viable option for saving on travel. Heavily demanded days of the week can typically drive up the prices you see. Booking your travel for a less competitive day can save up to 85% on the overall cost on flights from Ontario to St. Louis.

How far in advance should I book a flight from Ontario to St. Louis?

Users have found that booking a flight from Ontario to St. Louis at least 48 days early can save you up to 128% on average compared to booking a flight this week. If booking 48 days before your flight isn’t an option for you, users have found flights from Ontario to St. Louis for as little as $480 when booking for a departure date within the next two weeks. You can also check prices now. Some users have found airline tickets as low as $628 for flights departing within the next 3 days.

What is the cheapest month to fly from Ontario to St. Louis?

The best pricing can be found in the month of January. Prices to St. Louis from Ontario average $415. You can even find prices in January for less than $415, as users have found deals to St. Louis from as low as $215. The month of July appears to be one of the more expensive times to travel to St. Louis from Ontario. Flying in the targeted month can save you up to 12%.

What is the cheapest time of day to fly from ONT to STL?

A simple way to save on the total cost of your ticket is to fly from Ontario to St. Louis in the evening. If you’re flexible enough to do this you can expect to save up to 44% on your trip compared to booking a flight at noon.

Cheap Ontario to St. Louis flights in June & July 2024

Find cheap flight options from Ontario to St. Louis specifically for the months of June and July 2024. Explore affordable fares based on user searches. Over the last 7 days, Cheapflights users made 3,020,828 searches. Prices were last updated on June 9, 2024.
These are some of the most attractive deals on flights from Ontario to St. Louis in 2024. More deals are always being added, so be sure to check back regularly.
Mon 6/1712:59 amONT - STL
1 stop11h 48mFrontier
Tue 6/257:29 pmSTL - ONT
1 stop19h 46mFrontier
Deal found 6/9$136
Mon 6/1712:59 amONT - STL
1 stop11h 48mFrontier
Fri 6/215:36 pmSTL - ONT
1 stop8h 04mFrontier
Deal found 6/8$138
Mon 6/1712:59 amONT - STL
1 stop11h 48mFrontier
Thu 6/207:29 pmSTL - ONT
1 stop15h 35mFrontier
Deal found 6/8$141
Tue 6/1810:42 pmONT - STL
1 stop10h 00mFrontier
Fri 6/215:36 pmSTL - ONT
1 stop8h 04mFrontier
Deal found 6/8$147
Thu 6/2010:29 pmONT - STL
1 stop11h 25mFrontier
Fri 6/215:36 pmSTL - ONT
1 stop8h 04mFrontier
Deal found 6/8$148
Mon 6/1712:59 amONT - STL
1 stop11h 48mFrontier
Sat 6/227:29 pmSTL - ONT
1 stop13h 34mFrontier
Deal found 6/8$151
Tue 6/1810:42 pmONT - STL
1 stop10h 00mFrontier
Sat 6/227:29 pmSTL - ONT
1 stop13h 34mFrontier
Deal found 6/8$152
Fri 6/2110:23 pmONT - STL
1 stop9h 06mFrontier
Sat 6/227:29 pmSTL - ONT
1 stop13h 34mFrontier
Deal found 6/8$154
Wed 7/315:16 pmONT - STL
1 stop25h 38mFrontier
Mon 8/127:51 pmSTL - ONT
1 stop18h 41mFrontier
Deal found 6/8$155

Ontario to St. Louis 2024 flight deals

Discover exclusive flight deals for travel between Ontario and St. Louis in 2024. Find excellent offers based on user searches. Over the last 7 days, Cheapflights users made 3,020,828 searches. Data last updated June 9, 2024.
These are some of the most attractive deals on flights from Ontario to St. Louis in 2024. More deals are always being added, so be sure to check back regularly.
Fri 8/1612:49 amONT - STL
1 stop6h 48mFrontier
Thu 8/297:29 pmSTL - ONT
1 stop19h 32mFrontier
Deal found 6/8$136
Mon 6/1712:59 amONT - STL
1 stop11h 48mFrontier
Fri 6/215:36 pmSTL - ONT
1 stop8h 04mFrontier
Deal found 6/8$138
Thu 8/151:10 pmONT - STL
1 stop19h 08mFrontier
Mon 8/197:29 pmSTL - ONT
1 stop19h 18mFrontier
Deal found 6/8$139
Fri 9/138:35 pmONT - STL
1 stop11h 43mFrontier
Mon 9/167:29 pmSTL - ONT
1 stop24h 40mFrontier
Deal found 6/8$140
Mon 6/1712:59 amONT - STL
1 stop11h 48mFrontier
Thu 6/207:29 pmSTL - ONT
1 stop15h 35mFrontier
Deal found 6/8$141
Tue 6/1810:42 pmONT - STL
1 stop10h 00mFrontier
Fri 6/215:36 pmSTL - ONT
1 stop8h 04mFrontier
Deal found 6/8$147
Thu 6/2010:29 pmONT - STL
1 stop11h 25mFrontier
Fri 6/215:36 pmSTL - ONT
1 stop8h 04mFrontier
Deal found 6/8$148
Mon 6/1712:59 amONT - STL
1 stop11h 48mFrontier
Sat 6/227:29 pmSTL - ONT
1 stop13h 34mFrontier
Deal found 6/8$151
Tue 6/1810:42 pmONT - STL
1 stop10h 00mFrontier
Sat 6/227:29 pmSTL - ONT
1 stop13h 34mFrontier
Deal found 6/8$152

Ontario to St. Louis flights leaving soon

Find last-minute flight options from Ontario to St. Louis for spontaneous travel. Discover available flights and compare prices based on user searches. Secure great deals and offers for spontaneous trips with quick booking options. Over the last 7 days, Cheapflights users made 3,020,828 searches. Data last updated June 9, 2024.
Have a look at some of the flights available from Ontario to St. Louis departing last-minute. Tip: verify your flight details before completing your reservation.
Mon 6/1712:59 amONT - STL
1 stop11h 48mFrontier
Tue 6/257:29 pmSTL - ONT
1 stop19h 46mFrontier
Deal found 6/9$136
Mon 6/1712:59 amONT - STL
1 stop11h 48mFrontier
Fri 6/215:36 pmSTL - ONT
1 stop8h 04mFrontier
Deal found 6/8$138
Mon 6/1712:59 amONT - STL
1 stop11h 48mFrontier
Thu 6/207:29 pmSTL - ONT
1 stop15h 35mFrontier
Deal found 6/8$141
Tue 6/1810:42 pmONT - STL
1 stop10h 00mFrontier
Fri 6/215:36 pmSTL - ONT
1 stop8h 04mFrontier
Deal found 6/8$147
Mon 6/1712:59 amONT - STL
1 stop11h 48mFrontier
Sat 6/227:29 pmSTL - ONT
1 stop13h 34mFrontier
Deal found 6/8$151
Tue 6/1810:42 pmONT - STL
1 stop10h 00mFrontier
Sat 6/227:29 pmSTL - ONT
1 stop13h 34mFrontier
Deal found 6/8$152
Fri 6/148:45 pmONT - STL
1 stop11h 57mFrontier
Sat 6/157:29 pmSTL - ONT
1 stop13h 34mFrontier
Deal found 6/9$184
Fri 6/1410:23 pmONT - STL
1 stop9h 06mFrontier
Sat 6/227:29 pmSTL - ONT
1 stop13h 34mFrontier
Deal found 6/8$188
Mon 6/179:36 pmONT - STL
1 stop15h 11mFrontier
Wed 6/197:29 pmSTL - ONT
1 stop20h 40mFrontier
Deal found 6/8$203

One-way flights to St. Louis from Ontario

Search for one-way flight options from Ontario to St. Louis. Find affordable one-way fares based on user searches. Compare prices and availability to plan your one-way journey according to your preferred dates and budget. Over the last 7 days, Cheapflights users made 3,020,828 searches. Data last updated June 9, 2024.
Users in need of a one-way flight from Ontario to St. Louis can choose from these deals. Users in need of a round-trip flight from Ontario to St. Louis instead should update the search form at the top of page.
Thu 6/2010:29 pmONT - STL
1 stop11h 25mFrontier
Deal found 6/8$73
Thu 6/2010:29 pmONT - STL
1 stop11h 25mFrontier
Deal found 6/9$74
Fri 6/148:45 pmONT - STL
1 stop11h 57mFrontier
Deal found 6/7$75
Sun 7/712:59 amONT - STL
1 stop6h 26mFrontier
Deal found 6/8$87
Fri 6/2812:49 amONT - STL
1 stop6h 40mFrontier
Deal found 6/8$89
Sun 6/3012:59 amONT - STL
1 stop6h 30mFrontier
Deal found 6/8$91
Tue 7/237:16 pmONT - STL
1 stop24h 15mFrontier
Deal found 6/8$92
Mon 7/112:59 amONT - STL
1 stop11h 48mFrontier
Deal found 6/8$93
Mon 7/112:59 amONT - STL
1 stop11h 48mFrontier
Deal found 6/8$95

Find flights from Ontario to St. Louis within your budget

Customize your flight search to find flights from Ontario to St. Louis that fit within your specific budget. Explore options based on user searches and filter the results based on your desired price range. Find flights that match your budget for a cost-effective journey. Over the last 7 days, Cheapflights users made 3,020,828 searches. Data last updated June 9, 2024.

Fly from

Any airport

Fly to

Any airport

Budget

$136 - $432

Route

Depart

Return

Price

OntarioLambert-St Louis

ONT - STL

ONTSTL

Ontario

Fri 8/16

1 stop6h 48m

Lambert-St Louis

Thu 8/29

1 stop19h 32m

$136

OntarioLambert-St Louis

ONT - STL

ONTSTL

Ontario

Wed 8/14

1 stop12h 04m

Lambert-St Louis

Mon 8/19

1 stop24h 40m

$138

OntarioLambert-St Louis

ONT - STL

ONTSTL

Ontario

Thu 8/15

1 stop19h 08m

Lambert-St Louis

Mon 8/19

1 stop19h 18m

$139

OntarioLambert-St Louis

ONT - STL

ONTSTL

Ontario

Fri 9/13

1 stop11h 43m

Lambert-St Louis

Mon 9/16

1 stop24h 40m

$140

OntarioLambert-St Louis

ONT - STL

ONTSTL

Ontario

Thu 6/20

1 stop11h 25m

Lambert-St Louis

Sat 6/22

1 stop13h 34m

$141

OntarioLambert-St Louis

ONT - STL

ONTSTL

Ontario

Tue 7/16

2 stops14h 59m

Lambert-St Louis

Thu 7/18

1 stop11h 22m

$348

OntarioLambert-St Louis

ONT - STL

ONTSTL

Ontario

Tue 7/9

1 stop5h 40m

Lambert-St Louis

Tue 7/9

1 stop7h 29m

$368

OntarioLambert-St Louis

ONT - STL

ONTSTL

Ontario

Thu 9/26

1 stop4h 59m

Lambert-St Louis

Wed 10/9

2 stops7h 50m

$377

OntarioLambert-St Louis

ONT - STL

ONTSTL

Ontario

Wed 9/4

2 stops14h 59m

Lambert-St Louis

Sat 9/7

1 stop9h 46m

$432

Flights are sorted by cheapest first

Deals found on 6/8

How far ahead should I book a flight from Ontario to St. Louis?

Use this chart to determine the optimal time to book a round-trip flight from Ontario to St. Louis. Price data was last updated on May 31, 2024.
The best time to book flights from Ontario to St. Louis is 36 days before your desired departure date. The cost of your flight will likely increase significantly if you book two weeks in advance of your flight.
Search Deals

What is the cheapest day to fly from Ontario to St. Louis?

Use this chart to determine the cheapest time to fly round-trip from Ontario to St. Louis. Price data was last updated on June 2, 2024.
Morning
Noon
Afternoon
Evening
All times are departure.
Travelers seeking maximum savings on their Ontario to St. Louis flight should consider departing on Saturday afternoons when fares are most often at their lowest. Tuesday at noon flights should be avoided if possible as fares are typically the most expensive at this time.
Search Deals

Best time to book a flight from Ontario to St. Louis

Have a flexible travel schedule? Discover the best time to fly to St. Louis from Ontario with our price prediction graph.
Estimated round-trip price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.

Temperature and rainfall in St. Louis by month

Plan your trip to St. Louis by taking into account the average temperature and rainfall totals by month.

STL

Temperature

32 - 80.6 °F

If weather is an important factor for your trip to St. Louis, use this chart to help with planning. For those seeking warmer temperatures, July is the ideal time of year to visit, when temperatures reach an average of 80.6 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 32.0 F).

Reviews of airlines servicing St. Louis

Get insights into the airlines that provide service to St. Louis. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to St. Louis. Reviews last updated June 9, 2024.
Read through reviews of airlines operating flights from Ontario to St. Louis, such as American Airlines, Frontier and Delta. In addition to providing an overall rating, users have also rated airlines in terms of entertainment options, comfort, food, crew/service, and boarding process.
Alaska Airlines
8.1
Very good
9,245 reviews

Food

7.3

Crew

8.6

Entertainment

7.3

Overall

8.1

Comfort

7.9

Boarding

8.2

Reviews

1 / 10

Paid a lot for our exit row seats and they weren’t that roomy.

Alaska Airlines
8.1
Very good
9,245 reviews
Alaska Airlines
8.1
Very good
9,245 reviews

Food

7.3

Crew

8.6

Entertainment

7.3

Overall

8.1

Comfort

7.9

Boarding

8.2

Reviews

1 / 10

Paid a lot for our exit row seats and they weren’t that roomy.

Delta
8.0
Very good
10,310 reviews
Alaska Airlines
8.1
Very good
9,245 reviews

Food

7.3

Crew

8.6

Entertainment

7.3

Overall

8.1

Comfort

7.9

Boarding

8.2

Reviews

1 / 10

Paid a lot for our exit row seats and they weren’t that roomy.

United Airlines
7.4
Good
10,661 reviews
Alaska Airlines
8.1
Very good
9,245 reviews

Food

7.3

Crew

8.6

Entertainment

7.3

Overall

8.1

Comfort

7.9

Boarding

8.2

Reviews

1 / 10

Paid a lot for our exit row seats and they weren’t that roomy.

American Airlines
7.3
Good
14,172 reviews
Alaska Airlines
8.1
Very good
9,245 reviews

Food

7.3

Crew

8.6

Entertainment

7.3

Overall

8.1

Comfort

7.9

Boarding

8.2

Reviews

1 / 10

Paid a lot for our exit row seats and they weren’t that roomy.

Frontier
6.2
Okay
3,975 reviews
Alaska Airlines
8.1
Very good
9,245 reviews

Food

7.3

Crew

8.6

Entertainment

7.3

Overall

8.1

Comfort

7.9

Boarding

8.2

Reviews

1 / 10

Paid a lot for our exit row seats and they weren’t that roomy.

Related info for your journey

Find useful and relevant information for your journey from Ontario to St. Louis. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

  • Can I find flights from Ontario to St. Louis for under $200 on Cheapflights?

    Yes, there are multiple flights from Ontario to St. Louis for under $200. The cheapest flight booked recently is on Frontier for just $136, but on average you can expect to pay $162.

  • Are there last-minute flights available from Ontario to St. Louis for under $200?

    There are currently 20+ open flights from Ontario to St. Louis within the next 7 days for less than $200.

  • What is the cheapest airline to fly from Ontario to St. Louis round-trip?

    Flying on Frontier is currently your cheapest option to St. Louis, with prices starting at $136. Frontier is priced at 60% lower than the current average price of a flight leaving 3 months from now.

  • What are the cheapest airlines to fly from Ontario to St. Louis one-way?

    The cheapest airlines for a one-way flight from Ontario to St. Louis are Frontier ($73), Delta ($176), and Alaska Airlines ($203).

  • What does ONT to STL mean?

    These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Ontario Airport to Lambert-St Louis Airport flight would often be abbreviated as a ONT to STL flight.

  • Can I find deals for flights from Ontario to St. Louis that include extra baggage allowance?

    The amount of baggage you can bring on your Ontario to St. Louis flight depends on the airline and the type of fare you've chosen. After entering your flight details, you'll be able to view the specific baggage policies for each deal in the search results. Keep in mind that certain deals may offer additional baggage allowance.

  • Can I find deals on flights from Ontario to St. Louis with specific airlines?

    Yes, Cheapflights allows you to browse and filter Ontario to St. Louis flight deals by airline. After entering your origin and destination, use the available filters to view flights offered by airlines.

  • Can I find deals for flights from Ontario to St. Louis that include hotel bookings?

    Yes. In addition to deals on Ontario to St. Louis flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from Ontario to St. Louis?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Ontario to St. Louis.

  • Can I find deals for business class flights from Ontario to St. Louis?

    Yes. Cheapflights offers flight deals from Ontario to St. Louis by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

  • Can I find deals for flights from Ontario to St. Louis that allow pets onboard?

    Many airlines flying from Ontario to St. Louis offer the option to travel with pets. After selecting a flight deal, you can find more information about the airline's pet policy on their official website or by contacting the airline directly. Please note that additional fees and restrictions may apply.

  • Can I find deals on last-minute flights from Ontario to St. Louis?

    Yes, you can often find last-minute deals on Ontario to St. Louis flights on Cheapflights. However, these deals can vary and may not always be available. We recommend checking back frequently or signing up for price alerts for the most up-to-date deals.

  • How recently were the Ontario to St. Louis flight deals updated?

    The Ontario to St. Louis flight deals you see on this page were last updated on 6/8.

  • What are the most popular airlines that fly from Ontario to St. Louis?

    Before booking your flight from Ontario to St. Louis check out the most popular airlines for this route: American Airlines, Delta or Frontier.

  • What is the cheapest month to book a flight from Ontario to St. Louis?

    Currently, September is the cheapest month in which you can book a flight from Ontario to St. Louis (average of $318). Flying from Ontario to St. Louis in July is currently the most expensive (average of $365). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

See more FAQs

Browse thousands of different options on Cheapflights for your next trip

Toggle through the tabs below to find thousands of options on Cheapflights for your next trip.

Alternative routes for Ontario to St. Louis
See prices for flight routes from nearby airports that may be better suited for you.

Los Angeles to St. Louis flights
Los Angeles to Kansas City flights
Ontario to Kansas City flights
San Francisco to Kansas City flights
San Francisco to St. Louis flights
Burbank to Kansas City flights
Santa Ana to St. Louis flights
Sacramento to Kansas City flights
Burbank to St. Louis flights
Oakland to Kansas City flights
Santa Ana to Kansas City flights
Sacramento to St. Louis flights
Las Vegas to St. Louis flights
San Francisco to Springfield flights
San Jose to Kansas City flights
San Diego to Kansas City flights
Long Beach to St. Louis flights
Los Angeles to Springfield flights
San Diego to St. Louis flights
Ontario to Springfield flights
Oakland to St. Louis flights
San Jose to St. Louis flights
Las Vegas to Kansas City flights
San Diego to Springfield flights
Sacramento to Springfield flights
Fresno to St. Louis flights
Palm Springs to Kansas City flights
Long Beach to Kansas City flights
Las Vegas to Springfield flights
Reno to Kansas City flights
Reno to St. Louis flights
Palm Springs to Springfield flights
Fresno to Kansas City flights
Burbank to Springfield flights
Fresno to Springfield flights
Santa Ana to Springfield flights
Arcata to Branson flights
Medford to St. Louis flights
Santa Barbara to Kansas City flights
Palm Springs to St. Louis flights
San Jose to Springfield flights
Medford to Kansas City flights
Santa Barbara to St. Louis flights
Monterey to Kansas City flights
Burbank to Columbia flights
Monterey to St. Louis flights
Reno to Springfield flights
Los Angeles to Joplin flights
Las Vegas to Columbia flights

Top 4 airlines flying from Ontario to St. Louis

Discover the top 4 airlines that operate flights from Ontario to St. Louis. Compare their services, reliability, and customer satisfaction ratings to choose the airline that best suits your travel preferences and needs. Over the last 7 days, Cheapflights users made 3,020,828 searches. Data last updated June 9, 2024.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$105Average$200FlexibilityNo cancel feeOn-time62%
DeltaCheapest$276Average$357FlexibilityNo cancel feeOn-timeN/A
American AirlinesCheapest$282Average$467FlexibilityNo cancel feeOn-time71%
United AirlinesCheapest$318Average$452FlexibilityNo cancel feeOn-time69%
Las Vegas to New York flights
Los Angeles to Baltimore flights
Maui to O'ahu flights
Boston to New York flights
Boston to Tampa flights
Los Angeles to Mexico City flights
Hartford to Orlando flights
Nashville to Knoxville flights
USA to New Zealand flights
Los Angeles to New Orleans flights
Ontario to Stockholm flights

Search flights from Ontario to St. Louis by cabin class

Find flights from Ontario to St. Louis, based on your preferred cabin class, be it economy, premium economy, business, or first class.
First Class
Business Class
Prem Econ Class
Economy Class

Hourly flight availability from Ontario to St. Louis

Find hourly flight availability from Ontario to St. Louis. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated June 9, 2024.
0%of flight departuresEarly morningMidnight to 6 am
100%of flight departuresMorning6 am to noon
0%of flight departuresAfternoonNoon to 6 pm
0%of flight departuresEvening6 pm to midnight
Midnight
6 AM
Noon
6 PM

Book a flight to one of these trending destinations

User searches for flights to these destinations increased 20% or more in the past 90 days compared to other destinations
Flights to Gaziantep
Flights to Miyakojima Hirara
Flights to Figari-Sud Corse
Flights to Mason City
Flights to Komatsu
Flights to Sendai
Flights to Rhinelander Oneida County
Flights to Constanţa Mihail Kogalniceanu
Flights to Brainerd Crow Wing County
Flights to Reus
Flights to Virac
Flights to Neiva La Marguita
Flights to Pellston Emmet County
Flights to Urumqi
Flights to Bastia Poretta
Flights to Samos
Flights to Hyannis Barnstable
Flights to Provincetown
Flights to Alghero-Fertilia
Flights to Laayoune Hassan I
Flights to Devils Lake
Flights to Vava'u Lupepau'U
Flights to Hakodate
Flights to Edremit/Korfez
100% Free
Cheapflights is completely free to use, so you can start saving the moment you arrive.
Book with Flexibility
Our users can plan ahead with confidence and find flights with no change fees
Travel Smart
Millions of people come to us for their flight needs every year. We help make travel planning easy by providing useful insights and data-driven graphs that can inform your decisions.
View all available airlines